/Engine/Source/Editor/SequencerCore/Public/MVVM/ViewModels/OutlinerViewModel.h
Retrieve a flat list of the root items in this outliner model
[TArrayView](API\Runtime\Core\Containers\TArrayView)< const [TWeakViewModelPtr](API\Editor\SequencerCore\TWeakViewModelPtr)< [IOutlinerExtension](API\Editor\SequencerCore\MVVM\Extensions\IOutlinerExtension) > > GetTopLevelItems() const